It doen'nt blow the fuse, just melts the plastic, so, I bought a new pack of fuses of Narva quality as I thought it might even be as simple as crap fuses. been 2 days and still on the same one, however I haven't reved pased 4.5k yet, might see what happens @ 8K

If it's done it a further 3 times after you replaced the alternator Pedro, you have a short somewhere that is causing it to draw more than the rated capacity of the fuse (10a from memory).

If the wiring is all intact and good, the alternator regulator failing has probably caused an internal short in the fuel pump (most likely in the armature windings).

I would look at the pump and the wiring circuit as SSS says. If the current draw is high, but not above the rated, it will heat the wiring and then ultimately the fuse. Think of what happens when you put big headlight globes with standard wiring.

A question to ask is how many pumps are you running off that circuit, what is the rated current draw for the pump, what is the rated capacity of the factory wiring and what other items are running off that circuit. If you identify there is too much current draw on the circuit, i would suggest rewiring the circuit, or running the pump from its circuit with a separate fuse.

This may simply be a something that is not new, but has been highlighted by the failure of the alternator. More work for you pedro.

I did look into the fuel pump wiring ages ago, as i was concerned the pump would not be getting enough volts, as the lph rating is often on 13 or 14v or so volts(only running 1 pump, the AEM 325 lph) and by the time it gets to the pump can sometimes be as low as 10v. I will check it out again soon and the pump, but for now the new bunch of Narva fuses seem to be holding ok.

If your fuel pump wiring is the standard wiring this will be the cause of the large voltage drop, and also the resultant fuse issue. You need to bight the bullet and run some good heavy gauge power from the battery through a separate fuse and relay to run your pumps. Utilise the standard pump wiring as your switching circuit for the relays. If the battery is in the boot, this will be very easy to do. Just make sure you put a fuse in the new supply power.